1. Field of the Invention
The present invention relates generally to the field of mixing apparatus, and more particularly to a mixing apparatus for liquids such as paint or the like.
2. Background of the Invention
A variety of paint mixers currently exist in the art. These range from paint mixers for relatively small paint cans ranging in size from one half pint to one gallon to heavy duty size mixers for mixing paint contained in five gallon pails. The mixers for smaller paint cans are those of the type generally found in retail stores where paint is sold. These mixers tend to be oscillatory or vibrating mixers which shake the can back and forth until the desired degree of mixing is obtained. The heavy duty industrial type paint mixers generally involve mixing motions other than simple oscillatory or vibrating movements. In fact many provide so-called gyroscopic movement of the paint can which rotates the paint can about a generally lateral axis, while simultaneously spinning the can about an axis perpendicular to the lateral axis. Such gyroscopic movement is generally accepted as the movement which provides the greatest mixing efficiency.
Existing apparatus for accomplishing such gyroscopic movement for heavy duty, industrial type mixers include a motor or other drive means and a plurality of drive belts for transferring the rotational motion of the motor shaft to the above axes for simultaneously rotating and spinning the can about those axes. Although these existing gyroscopic mixers provide generally acceptable mixing, maintenance costs tend to be a significant factor because of the relatively short life span of the drive belts. This is a particularly significant factor when the mixer is being used for heavy duty applications. In addition to the actual cost and expense relating to replacement of the belts, a cost is also associated with the downtime of the mixer during such replacement. Further, although unexpected downtime can be minimized with regular maintenance, the possibility continues to exist that a belt will unexpectantly break, resulting in unexpected downtime and inconvenience.
Present pain mixers, both those designed for smaller cans as well as those designed for heavy duty application, are provided with paint can clamping or gripping members which include a bottom pallet and a top lid which are moved vertically relative to one another to clamp or release a paint can. In other words, to clamp the paint can between the pallet and lid, the lid is moved vertically downwardly, usually as a result of rotating a threaded member, until the lid engages the top of the paint can and clamps the can between the lid and the pallet. After the mixing is complete, the lid is moved vertically away from the top of the paint can so that the paint can be removed. Usually the lid is raised just enough to allow the paint can to be removed in a generally lateral or horizontal direction relative to the axial axis of the paint can.
This is generally not a problem with respect to smaller paint cans of one gallon and smaller. However, it is a much greater problem with larger paint cans such as five gallon cans. A five gallon can, filled with paint, can weigh as much as 100 pounds. Thus, it is often difficult for the operator of the mixer to lift the can vertically and then move it horizontally into the relatively small area between the pallet and the lid. One limited solution to this problem is to raise the lid vertically as high as possible to provide a greater area within which to set the can between the pallet and the lid. However, this requires a larger apparatus to accommodate the additional desired movement of the lid, and also requires additional time to raise and lower the lid to provide such additional space. Even with this additional vertical movement of the lid, there is a limit to the advantages that can be obtained.
Accordingly, there is a need in the art for mixing apparatus, and particularly a paint mixer designed for heavy duty industrial or commercial applications which minimizes, if not eliminates, the maintenance problems that exist with current mixers. A need also exists for a mixing apparatus which provides an easier and improved means for introducing a paint can into, and removing a paint can from, the area between the pallet and the lid.